Evaluation of Interface Strength between a Copper Submicron Dot and Silicondioxide Substrate

Abstract

An experimental evaluation method of interface strength between ductile submicron-dots and a hard substrate is developed. The validity is examined with copper (Cu) cylindrical dots of submicron scale on a silicondioxide (SiO₂) substrate. A hard-layer of tungsten (W) is employed to restrain the deformation and concentrate the stress near the free-edge of Cu/SiO₂. A diamond tip is dragged horizontally along the SiO₂ surface and the load is applied to the side edge of the W layer at a constant displacement rate using a modified atomic force microscope. Both the lateral and the vertical loads and displacements are continuously monitored during the test. After the tip hits the W layer, the lateral load, F_l, increases almost proportionally with the lateral displacement, δ₁. The Cu dot with the W layer then is clearly separated from the SiO₂ along the interface. The restraint by the W layer works well so that there are little damages in both the delaminated W/Cu dot and the substrate. The delamination lateral load, F_lC, is successfully evaluated.